Sludge Strider

The drain trigger fires on entry and exit both, which is the structural tell of what this creature is built to reward: not a board of expensive artifacts but a churning supply of cheap, disposable ones. Each Servo or Thopter token that enters, each artifact you sacrifice, each one you blink, becomes a one-mana payment for a point of life swing. The cost per trigger is the brake on what would otherwise be a runaway engine; it ties the drain to mana you have available, so a turn with three artifacts entering and leaving is only as good as your ability to pay for it. As a four-mana Esper build-around it sits in the artifact-aristocrats lineage, where artifacts are fuel rather than payoff, and the body itself is incidental: a 3/3 is just enough to hold the ground while the engine does the killing one life at a time. What keeps the design coherent is the symmetry of the trigger window. Decks that already want to recur, sacrifice, or flicker their artifacts get a drain attached to motion they were making anyway, turning value loops into incremental damage. It asks you to build a deck where artifacts are always in transit, then taxes that transit just enough that the engine never outruns your mana.